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Old 02-14-2018, 03:40 PM   #1
3 Rivet Member

1959 24' Tradewind
Twin Falls , Idaho
Join Date: Jul 2015
Posts: 154
Pressurize Gray Tanks

Anyone pressurize the tanks before. Wanted to see if there was going to be any leaks, soaped up the fittings and no bubbles.
The regulator I have doesn't register (it seems) until it gets about 5psi. As you can see in the before and after, the tanks started to bulge and I was afraid to put too much stress on them and the needle on the regulator didn't move at all.

Seeing them bulge is a little disconcerting to me, think it may put some stress on the belly pan if I can't dump right away. Should I be concerned? Thought about changing out the straps I used for some thicker ones but I don't think it will make a difference unless their really thick.
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Trons4u is offline   Reply With Quote
Old 02-14-2018, 03:56 PM   #2
4 Rivet Member
Byron Center , Michigan
Join Date: Aug 2017
Posts: 275
They're not designed for pressure, so I would hesitate to put any on them. Nothing quite like a vessel rupturing under pressure... Fill them with water (their natural state) and let it sit overnight. If they leak, you have a leak. :-)
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Old 02-14-2018, 04:50 PM   #3
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2016 28' International
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Las Vegas , Nevada
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You need to do the opposite, pull a vacuum on the tank and see if it falls. draw system down to no more than 4-5hg and let sit for awhile, if the vacuum falls you have a leak.
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Old 02-14-2018, 05:36 PM   #4
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2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 8,439
Keep in mind wastewater and fresh tanks are NOT designed to be heavy enough to pressurize much or draw a vacuum on them. When mounted for use, they are supported from the bottom by the pan, and usually supported on the sides by the rest of the enclosure or frame members.

I would fill them up to the max once supported as installed and the outlet is plumbed, and then just look for any leaks after they sit overnight...
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Old 02-14-2018, 08:55 PM   #5
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1975 27' Overlander
Conifer , Colorado
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I worked in a rotomolding shop for a few years. We pressure leak tested every tank we molded. We used "propane" regulators and induced 2 psi in the tanks. They will bulge out some. We then dunked them in big tanks of water. I do not know what pressure a polyethylene tank will rupture.

I don't pressure test at home. I simply fill my tanks full of water and come back in a few days. Expect to see the floor dry.

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Old 02-15-2018, 10:38 AM   #6
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1959 24' Tradewind
Twin Falls , Idaho
Join Date: Jul 2015
Posts: 154
Thanks all. I didn't use water because at the moment I have nowhere to drain it. I went back the next day to check if they were still pressurized and they were. So that was good to see.

I was mostly concerned with the way they bulge and if they did that when filled with water. Didn't want the belly pan popping rivets.

Thanks again
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